Jane finds a lost leopard cub and decides to keep it, but Tarzan won't like having a leopard around.

Two deserters of the French Foreign Legion called Hooft and Hugo flee into the jungles of Africa. Unfortunately, their former superior, Lt. Colonel Staquait, finds their tracks and vows to follow them to the ends of the earth. Tarzan rescues the deserters from the perils of the jungle and the duo begin taking advantage of the resulting hospitality. Jane, being suspicious of the parasitic pair and their fantastic stories, decides to turn them in, only to realize who the real criminal is.

Tantor drinks water from the river and gets ill. Tarzan, Jane, and the Professor go upstream to find out what's poisoning the river while Terk tries to save Tantor. Along the way, they lose their boat and get captured by a group of natives who blame them for poisoning the river.

The Professor and Jane figure out that it's a mine that's poisoning the river and that Tarzan and the native warrior are in trouble. Tantor, Terk, Jane and the Professor come up with a plan and must work together with the natives to save Tarzan and get rid of the mine once and for all.

Poachers arrive in the jungle and are setting traps everywhere, so Tarzan warns everyone to be careful. Meanwhile, Terk encourages Tantor to act on his attractions to a female elephant named Dania with a talent for singing. The first date goes well, and though everybody finds Dania perfectly charming, she herself gets off on the wrong foot with Terk. When Terk discovers Tantor would rather spend his time with Dania than her, she plans to break them up, but ends up getting caught in one of the poachers' traps instead. Now Tantor must decide which is more important to him—his relationship with the difficult Dania, or saving his best friend from being kidnapped.

The jungle is visited by the former President Teddy Roosevelt and, while on the hunt for animal specimens to study (which Tarzan heavily disapproves of), both are kidnapped by conspirators. In the process of escape, Tarzan teaches the President the importance of respecting nature, and he gains a new appreciation for it by the time he leaves, promising to bring that lesson home to America.

The Professor learns about a spiritual silver ape that, supposedly, cures the injured of the jungle. Not believing this is a spiritual creature, he plans to study it more. But when Philander steals his notes and finds out about the ape, he plans to capture it.

Terk gets scared when she sees a monster, which is later revealed to be a velociraptor from Pellucidar. The others initially dismiss Terk, but believe her after the dinosaur attacks the Professor's camp as well as Tarzan and Jane's treehouse. Tarzan attempts to find out how the velociraptor managed to get out of Pellucidar and how it can be sent back.

Tarzan helps the people on an sinking schooner escape. He discovers the passengers are Jane's friends Eleanor, Hazel, and Greenly, as well as Greenly's fiancé Henry. Eleanor and Hazel do not think Henry is "well-rounded" enough, hoping the jungle and Tarzan can toughen him up. Eventually Henry's toughness is put to the test when an earthquake, followed by a tidal wave, hits the jungle.

Clayton's sister kidnaps Jane, Tantor, Terk, and the Professor, placing each in a separate, deadly peril. She then injects Tarzan with a fatal poison via blowdart and informs him that the antidote lies far away on a distant mountain she's dubbed "Clayton's Peak". He, therefore, has a choice—to suffer as she had and lose those he loves, or as Clayton had and lose his own life.

A writer named Ed is in desperate need of some inspiration for his next novel. He finds it while walking down the street in the form of a newspaper article about Tarzan, "The Missing Link". He begins tracking down various leads to Tarzan's whereabouts, including Tarzan's friends and enemies. They all tell Ed of their first encounters with Tarzan, prompting Ed to head out into the jungle to find Tarzan himself.

Jane's friends, Eleanor, Greenly, and Hazel, thinking Jane is in trouble, come to rescue her. When they find her and everything is explained, they fret Jane has changed. To prove she hasn't, Jane takes them on a picnic in the jungle. That's when trouble comes up.